Yesterday, I faced the problem while I was trying to install ubuntu with Windows 7 for dual-boot.
The problem is ubuntu cannot see any partition on my hard disk even I’ve parted it to 3 partitions
and 1 of 3 partition has been installed Windows 7 already.

I’ve tried many ways to solve this issue and google for more than 3 hours to find the solution.
But bad luck for me, there is no any solution and the root cause is not out there.

Finally, I’ve found the root cause myself.

The problem come from the day before that I tried to install Mac OS X on my dell laptop and in the installation process, it change my hard disk to be GUID Partition Table (GPT).
And this partition type cannot install windows 7 32-bit on it. So when I tried to install windows 7, the windows has change structure of hard disk  to be some thing that ubuntu installer cannot read the actual partition. And if I use ubuntu to part the partition, the Windows 7 installer will not be able to install on any partition.

SO the solution is to use GParted in ubuntu Live CD to change the partition table to be Master Boot Record (MBR) and then everything works like a charm.

Very easy, right?

Hope this can help anyone who faces the same problem as me.